Business Segment Information (Market Segment Financial Results) (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Net interest income (expense)		$ 544	$ 586	$ 603	$ 606	$ 614	$ 599	$ 549	$ 590	$ 2,339		$ 2,352		$ 2,061
Provision for credit losses										74		(1)		74
Noninterest income										1,010		976		1,107
Noninterest expenses		451	435	424	433	448	452	446	448	1,743		1,794		1,860
Provision (benefit) for income taxes		(82)	(80)	(87)	(85)	(90)	(63)	(54)	(93)	(334)		(300)		(491)
Net income (loss)		$ 269	$ 292	$ 298	$ 339	$ 310	$ 318	$ 281	$ 326	1,198		1,235		743
Net loan charge-offs (recoveries)										107		51		92
Assets, average										71,488		70,724		71,452
Loans, average										50,511		48,766		48,558
Deposits, average										$ 55,481		$ 55,935		$ 57,258
Return on average assets	[1]									1.68%		1.75%		1.04%
Efficiency ratio	[2]									51.82%		53.56%		58.70%
Michigan
Net interest income (expense)										$ 729		$ 727		$ 657
Provision for credit losses										(11)		30		8
Noninterest income										291		296		324
Noninterest expenses										554		577		589
Provision (benefit) for income taxes										(108)		(90)		(137)
Net income (loss)										369		326		247
Net loan charge-offs (recoveries)										11		7
Assets, average										13,157		13,207		13,393
Loans, average										12,553		12,531		12,676
Deposits, average										$ 20,081		$ 20,770		$ 21,818
Return on average assets	[1]									1.77%		1.51%		1.09%
Efficiency ratio	[2]									54.02%		56.22%		60.01%
California
Net interest income (expense)										$ 811		$ 788		$ 711
Provision for credit losses										(33)		26		101
Noninterest income										173		164		171
Noninterest expenses										406		424		404
Provision (benefit) for income taxes										(155)		(123)		(145)
Net income (loss)										456		379		232
Net loan charge-offs (recoveries)										8		27
Assets, average										18,856		18,544		18,269
Loans, average										18,540		18,283		18,008
Deposits, average										$ 16,857		$ 16,964		$ 17,533
Return on average assets	[1]									2.42%		2.04%		1.25%
Efficiency ratio	[2]									41.21%		44.58%		45.83%
Texas
Net interest income (expense)										$ 493		$ 474		$ 451
Provision for credit losses										119		(53)		(72)
Noninterest income										128		130		131
Noninterest expenses										345		365		375
Provision (benefit) for income taxes										(38)		(64)		(104)
Net income (loss)										119		228		175
Net loan charge-offs (recoveries)										93		12
Assets, average										11,269		10,380		10,434
Loans, average										10,616		9,812		9,960
Deposits, average										$ 8,780		$ 8,992		$ 9,623
Return on average assets	[1]									1.06%		2.20%		1.61%
Efficiency ratio	[2]									55.59%		60.30%		64.35%
Other Markets
Net interest income (expense)										$ 373		$ 353		$ 316
Provision for credit losses										(5)		(1)		36
Noninterest income										365		359		423
Noninterest expenses										369		376		450
Provision (benefit) for income taxes										(74)		(60)		(71)
Net income (loss)										300		277		182
Net loan charge-offs (recoveries)										(5)		5
Assets, average										9,599		8,922		8,584
Loans, average										8,802		8,140		7,914
Deposits, average										$ 7,905		$ 8,144		$ 7,881
Return on average assets	[1]									3.13%		3.11%		2.12%
Efficiency ratio	[2]									50.03%		52.93%		60.98%
Finance & Other
Net interest income (expense)										$ (67)		$ 10		$ (74)
Provision for credit losses										4		(3)		1
Noninterest income										53		27		58
Noninterest expenses										69		52		42
Provision (benefit) for income taxes										41	[3]	37	[3]	(34)
Net income (loss)										(46)		25		(93)
Net loan charge-offs (recoveries)										0		0
Assets, average										18,607		19,671		20,772
Loans, average										0		0		0
Deposits, average										$ 1,858		$ 1,065		$ 403

[1] Return on average assets is calculated based on the greater of average assets or average liabilities and attributed equity.

[2] Noninterest expenses as a percentage of the sum of net interest income and noninterest income excluding net gains (losses) from securities and a derivative contract tied to the conversion rate of Visa Class B shares.

[3] Primarily reflected discrete tax items, including benefits of $17 million and $48 million in 2019 and 2018, respectively, and a net charge of $72 million in 2017.